Not only does it look like he's added some neat fluid-dynamics based particle simulation on top of Synthesia's existing spark effects, but there also appears to be some custom-timed/coordinated real-life lighting effect involved in getting the note colors to shine on his fingers (and the keys) realistically. Whatever he's doing, it took a lot of work and the results look pretty amazing.

That kind of effect is something we could consider for a future update of the Synthesia Video Creator. (I've been looking for an excuse to tinker with a Navier-Stokes simulation for the better part of two decades now!) If the simulation is fast enough to run in real-time, it might even make sense to enable it in the main Synthesia client for interactive use, too.

That said, I can't promise anything anytime soon. The upcoming Synthesia 11 release has our full attention at the moment.